It is often necessary to make field tests of the pressure at various points within a turbine-powered generating system. For this purpose, pressure transducers (or "pressure transmitters") are often installed on the turbine and around the turbine power plant at specific locations, depending upon where pressure measurements are needed. The pressure transducers provide voltage signals indicative of the measured pressure. Means are generally provided external to the turbine for coupling the transducers, via a cable, to a data acquisition unit which is capable of receiving and processing the pressure signals. Typically, the pressure signals are in the range of 0.2-1.0 VDC.
The transducers typically require an input voltage of approximately 24 VDC to operate, but they will generally continue to function when the input voltage varies from approximately 15 to 30 VDC. The input power to the pressure transmitters is obtained by transforming and rectifying the nearest available source of line power. For this purpose, it is generally necessary for the individual conducting the field test to bring along a portable DC power supply. The power supply must of course be compatible with the available line power. For example, a field test conducted on a turbine generator located in Spain would require a power supply capable of converting 220 to 240 VAC at 50 Hz to 24 VDC, while a field test on a turbine generator located in the United States would require a power supply capable of converting 110 to 120 VAC at 60 Hz to 24 VDC. Power supply modules are known in the art that are capable of being easily adapted to function off of any of the above conditions. These devices can become burdensome and expensive, however, particularly when it is desired that many pressure transmitters be powered at once. For example, in some systems it is necessary to simultaneously measure the pressure at up to twenty-five points.
It would therefore be desirable to provide means for providing DC power to a plurality of transducers or like elements, such as pressure transmitters. The power supply will preferably be capable of easy adaptation to line power supplies of 110-120 VAC or 220 to 240 VAC, at either 50 or 60 Hz. Most preferably, the power supply will be built into a universal interface apparatus wherein means are provided for receiving pressure data from the plurality of pressure transmitters and providing this data to a data acquisition unit over a single multi-conductor cable. Such an apparatus would reduce the amount of equipment required for field performance testing of turbines, with an attendant saving of cost, manpower, and time. The present invention achieves these goals.